Plastics are, generally, easier to form than glasses and metals, can be easily formed into a variety of shapes and have, therefore, been used in a variety of applications. Specifically, plastics are representatively used in a field of containers such as bottles and packings such as caps fitted to the containers.
Here, when a liquid is contained in the container, there inevitably arouses a problem of liquid dripping. Therefore, a contrivance is required such that, when the liquid contained in the container is to be poured out through a spout or a pouring nozzle of the cap, the liquid being poured out does not drip out creeping along an outer wall surface of a pouring port.
Various means have been proposed in an attempt to prevent the dripping of liquid. For instance, a patent document 1 is proposing a means of coating the pouring port with a fluorine-contained resin, and a patent document 2 is proposing a means of forming a rough surface in the pouring port.